The present invention relates in general to coupling means for coupling portions of a subsea riser to a floating vessel or overhead platform where a riser connection is made with a subsea well. More particularly, the present invention is directed to a method and apparatus for retaining the upper tube of a telescopic joint in the riser installation to a cross over support conduit secured to the vessel or platform in a manner which facilitates the subsequent disengagement of the joint upper tube therefrom.
In subsea well operations where a riser connection is established between a floating vessel or an overhead platform and a subsea well, as in prior U.S. Pat. No. 3,791,442, it is conventional to employ a telescopic joint wherein major portions of the riser are suspended by riser tensioning means which allow compensating movement of the vessel or platform under wind or sea action relative to the major extent of the riser. As in said U.S. Pat. No. 3,791,442, an upper, usually inner, tube of the telescopic joint is connected to the vessel or platform, which such connection possibly including a ball and socket conduit connection assembly supported from a diverter assembly landed in a support structure beneath the rotary table on the vessel or platform. It has been conventional heretofore to engage the telescopic joint upper tube to a cross over or support conduit suspended from the vessel or platform associated conduits by a threaded engagement between the upper tube and cross over support conduit. However, after continued use of the riser in the corrosive environment of salt water ocean situations it has been found difficult to disengage the telescopic joint upper tube from its associated support conduit to which it is threadably engaged.
It is therefore the primary object of the present invention to disclose and provide a method and apparatus for providing a threaded interengagement between the telescopic joint upper tube and the associated cross over support conduit by which the upper tube is suspended from the overhead vessel or platform in a reliable secure manner and yet will facilitate the subsequent removal of the upper tube of the telescopic joint subsequent to extensive use even if the threaded engagement has become worn or corroded in such a manner as to preclude or inhibit a rotational disengagement.